The Bag-Valve-Mask (BVM) device is a handheld manual resuscitator used to deliver positive pressure ventilation to patients who are not breathing adequately. Composed of a self-inflating bag, a one-way valve, and a face mask, the primary challenge of BVM use is achieving and maintaining a tight, leak-free seal against the patient’s face. A poor seal allows air to escape, significantly reducing the volume of air delivered to the lungs and making ventilation ineffective.
Airway Preparation Before Mask Placement
Effective ventilation with a bag-mask device begins with ensuring an open airway. The soft tissues in the mouth and throat, primarily the tongue, can easily obstruct the passage of air when a person is unconscious. This obstruction must be relieved before a proper seal can translate into effective lung inflation.
One fundamental step involves positioning the patient’s head to align the airway axes, often referred to as the “sniffing position.” This maneuver typically involves elevating the head while tilting the chin upward, which physically moves the tongue and soft palate away from the back of the throat. In cases where a neck injury is suspected, a modified jaw thrust maneuver is used to lift the jaw forward without tilting the head.
Using airway adjuncts such as the Oropharyngeal Airway (OPA) or Nasopharyngeal Airway (NPA) is also highly recommended to maintain patency. The OPA is inserted into the mouth of an unconscious patient without a gag reflex to keep the tongue secured forward. The NPA is a soft rubber tube inserted through the nostril, better tolerated in semi-conscious patients or those who still have an intact gag reflex. Both devices bypass the most common anatomical obstructions, making the subsequent mask seal far more likely to result in successful ventilation.
Proper selection of the mask size is also a prerequisite for a successful seal. A mask that is too large or too small will inevitably leak. The correct mask should cover the bridge of the nose, fit snugly between the lower lip and chin, and encompass the mouth and nose entirely. Leaving dentures in place, if present, can actually help provide a more rigid facial structure, which assists in forming a better seal.
The Standard E-C Clamp Technique
Once the airway is open and the correct mask is chosen, the standard method for a single rescuer to secure the mask and maintain the airway is the E-C clamp technique. This method uses one hand to perform two distinct, simultaneous actions: sealing the mask and lifting the jaw. The non-dominant hand is typically used for this complex task, leaving the dominant hand free to squeeze the bag.
The technique involves placing the thumb and index finger on the mask dome to form the letter “C.” These two digits are responsible for applying downward pressure to the mask, ensuring the edges are firmly seated against the contours of the face, particularly over the bridge of the nose and the chin. The downward force must be consistent to prevent air from escaping around the perimeter of the mask.
The remaining three fingers—the middle, ring, and little fingers—form the letter “E” and are positioned beneath the bony prominence of the patient’s jaw, or mandible. These “E” fingers are tasked with performing the jaw thrust maneuver. They lift the jaw upward and forward, which helps to maintain the open airway established during the preparation phase.
The success of the E-C clamp relies on the coordinated opposition of these forces: the “C” pushing the mask down onto the face, and the “E” pulling the jaw up into the mask. This dual action effectively sandwiches the face between the mask and the jawbone, creating a tight seal while actively maintaining the airway. Rescuers must ensure the “E” fingers grasp the jawbone itself, avoiding pressure on the soft tissues under the chin, which could inadvertently compress the airway.
The rescuer should position themselves directly at the patient’s head to optimize leverage and ensure the mask’s apex is over the bridge of the nose. The pressure applied must be forceful enough to overcome the natural resistance of the face and jaw. This single-handed technique is physically demanding and requires continuous, focused effort to sustain the necessary seal and upward jaw lift.
Troubleshooting a Leaking Seal
Despite proper technique, a bag-mask seal may leak, which is typically indicated by a lack of visible chest rise or an audible hissing sound as air escapes. The first step in troubleshooting is to immediately re-evaluate the patient’s head position. A slight shift in the patient’s head or neck can cause the tongue to fall back, which mimics a leak by preventing air from entering the lungs.
If the head position is correct, the next action is to slightly increase the upward lift applied by the “E” fingers on the jaw. Increasing the force of the jaw thrust can often resolve minor leaks by tightening the seal between the mask and the face, and further opening the upper airway. The rescuer should also check the mask placement to confirm the triangular shape is correctly seated over the nose bridge and the chin.
If the seal remains inadequate, the rescuer should consider the possibility of an incorrect mask size and, if available, switch to a smaller or larger option. In cases of patients with beards or those who are edentulous (lacking teeth), keeping the seal becomes more difficult. For edentulous patients, leaving their dentures in can help, while beards may require pressing the mask more firmly into the facial hair or applying a water-soluble lubricant to the edges of the mask to improve the contact surface.
Finally, the manner of delivering the breath can influence the integrity of the seal. Delivering a quick, forceful squeeze on the bag can cause a rapid pressure spike that forces air out through any minor gap in the seal. Instead, the rescuer should aim for a slow, smooth squeeze over approximately one second. This allows the pressure to increase gradually and minimizes the likelihood of a high-pressure leak. If a single rescuer cannot achieve an effective seal despite these adjustments, a two-person technique is the most effective solution, where one rescuer uses both hands to maintain the seal and jaw lift while the second squeezes the bag.